The present invention relates to rear axle systems for bicycles.
Prior art bicycles have employed through-axle systems for both front and rear axles. For example, U.S. Pat. No. 7,654,548 and U.S. Patent Publication No. 2009/0072613 each disclose an axle securing structure that includes two lips that define slots for receiving a portion of a wheel hub, and holes in the frame dropouts for receiving a axle. The axle is inserted through the hole in one of the dropouts, through an opening on the hub, and is then threaded into the other dropout. The axle can include a quick-release mechanism that facilitates toolless insertion and removing of the axle.
When utilized on a rear wheel of a bicycle, the slots define a hub spacing, and the lips (which define the slots) determine a clearance width less than the hub spacing. For example, in one conventional arrangement, the hub spacing is 142 mm and the clearance width is 135 mm, due to the fact that the lips each have a length (parallel to the axle) of 3.5 mm.